The present invention generally relates to an implantable cardiac lead for use with an implantable cardiac stimulation device. The present invention more particularly relates to such a lead adapted for use in the coronary sinus region of a heart and which includes all necessary electrodes for both defibrillation and pacing.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Traditionally, therapy delivery had been limited to the venous, or right side of the heart. The reason for this is that implanted electrodes can cause blood clot formation in some patients. If a blood clot were released arterially from the heart left side, as for example the left ventricle, it could pass directly to the brain potentially resulting in a paralyzing or fatal stroke. However, a blood clot released from the right heart, as from the right ventricle, would pass into the lungs where the filtering action of the lungs would prevent a fatal or debilitating embolism in the brain.
Recently, new lead structures and methods have been proposed and even practiced for delivering cardiac rhythm management therapy to the left heart. These lead structures and methods avoid direct electrode placement within the left atrium and left ventricle of the heart by lead implantation within the coronary sinus region of the heart. As used herein, the phrase xe2x80x9ccoronary sinus regionxe2x80x9d refers to the venous vasculature of the left ventricle, including any portions of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus.
It has been demonstrated that electrodes placed in the coronary sinus region of the heart may be used for left atrial pacing, left ventricular pacing, and cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of a patient population with left ventricular dysfunction and/or congestive heart failure which would benefit from left heart side pacing, either alone or in conjunction with right heart side pacing (bi-chamber pacing), and/or defibrillation.
Cardiac leads intended for use in providing both cardiac pacing and defibrillation in the left heart via the coronary sinus region are difficult to position due to the tortuous venous routes of the human anatomy. Moreover, to provide both pacing and defibrillation of both the left atrium and the left ventricle from the coronary sinus region with multiple leads employing the appropriate types of electrodes is extremely difficult given the space constraints to accommodate multiple leads in the coronary sinus region. Hence, such implants are too cumbersome, difficult, and time consuming to perform and would likely result in compromised performance or system malfunction.
The present invention provides a single cardiac lead for implant in the cardiac sinus region of the heart. The lead includes all of the electrodes necessary for atrial pacing and defibrillation and ventricle pacing and defibrillation from the coronary sinus region. As a result, with the lead of the present invention, the implanter seeking such combined functionality need only implant a single lead.
In accordance with the present invention, the lead includes an elongated lead body having a distal end and a proximal end. A first electrode assembly including at least one pacing electrode and a defibrillation electrode is positioned at the distal end of the lead body. A second electrode assembly including at least one pacing electrode and a defibrillation electrode is positioned on the lead body proximal to the first electrode assembly. A further defibrillation electrode is positioned on the lead body proximal to the second electrode assembly. The first and second electrode assemblies and the further defibrillation electrode are spaced apart so that when the lead is implanted in the coronary sinus region of the heart with the first electrode assembly adjacent the left ventricle, the second electrode assembly is adjacent the left atrium and the further defibrillation electrode is within the right atrium and/or superior vena cava of the heart. The at least one pacing electrode of the first electrode assembly may be used to pace the left ventricle. The at least one pacing electrode of the second electrode assembly may be used for atrial pacing. The defibrillation electrode of the first electrode assembly together with the further defibrillation electrode may be used for ventricular defibrillation and the defibrillation electrode of the second electrode assembly together with the further defibrillation electrode may be used for atrial defibrillation.
The lead may further include a plurality of terminals and conductors for connecting the electrodes to an implantable cardiac stimulation device.
Further, the present invention provides a method of making the lead.